REPRODUCTION AND FERTILITY
CHAPTER 2 – FEMALE ANATOMY
Components of the female reproductive system:
Two ovaries
Primary reproductive organs, located in the abdominal cavity. They produce female reproduction hormones
(estrogens and progesterone) and contain the oocytes. The shape and size of the ovaries are strongly
dependent on the activity of the pituitary land that produces LH and FSH, which stimulate follicle
development, ovulation and corpus luteum development.
Reproductive tract
It is a tubular structure consisting of (from inside to outside):
- Endometrium a mucosa layer of epithelial cells and a submucosa layer containing blood vessels
and uterine glands
- Myometrium two muscle layers consisting each of an intermediate layer rich in blood vessels, a
circular layer of smooth muscle and a longitudinal layer
- Mesometrium serosa layer of connective tissue
The length of the reproductive tract depends on species, e.g. the oviduct can be 15-30cm based on species,
uterus horns are longest in sows (60-90cm), vagina can be 10-35cm.
Different parts of the tract:
- Oviducts long and coiled tubes that connect the ovaries to the uterus. It can be divided into:
o Infundibulum the abdominal end on the oviduct (ovarian bursa), with fimbriae that
surround the ovaries
o Ampulla more distal part of the oviduct (it is right after the infundibulum near the
ovaries), where fertilisation takes place
o Isthmus the last part connected to the uterus with the utero-tubal junction UTJ
- Uterus consists of two uterine horns (cornua uteri), a uterine body (corpus uteri) and the cervix.
The relative size of the uterine body and the horns varies between species. There are different
types of uteri:
o Uterus duplex both horns are completely split, no uterine body is present and there are
2 cervices, e.g. in rabbit
o Uterus bicornuate with two poorly developed (mare), moderately developed (cow) or
highly developed (sow, bitch, queen) uterine horns. There is only one cervix
o Uterus simplex with a prominent uterine body and no uterine horns (humans).
The endometrium is important to regulate cyclicity and embryonic development. The glands of the
endometrium are in the epithelium of the uterus; they are small during oestrus but grow and
increase their secretions during progesterone dominance. Also the endometrium itself produces
secretions important for survival and capacitation of sperm cells, development of embryo and
luteolysis (elimination of corpus luteum if there is no pregnancy).
The endometrium of the cow and ewe contain about 100 non-glandular protrusions called
caruncles, important for adhesion of the placenta during pregnancy. The myometrium is important
for transport of sperm cells and expulsion of foetus.
, Functions of the uterus sperm transport to oviducts, transport of embryo to the site of
implantation, luteolysis and control of cyclicity, providing nutrition and gas exchange to the
embryo, expulsion of foetus at parturition.
- Cervix it has a thick muscular wall and is a sphincter-like organ. It is a barrier that closes the
connection between uterus and environment, because smooth muscles in it contract to prevent
passage of microorganisms. It has many folds which can be in a spiral (ruminants) or adapted to the
corkscrew-like penis of pigs. It also has many glands that produce mucus; during pregnancy, a thick
mucus closes the cervix to prevent bacterial entrance in the uterus.
Functions semen transport, semen reservoir, selection of fertile sperm cells.
- Vagina connects cervix and outer genital opening. It does not have many glandular cells and the
musculature is less developed. The caudal end of the vagina hosts the opening of the urethra. In
cattle and sheep, semen is deposited here while in pigs it is deposited in the cervix and in horses in
the uterus. The vagina also can act as barrier against microorganisms. Most animals have only one
vagina, but marsupials have two: one to transport sperm and one to transport the embryo to the
pouch.
External genitalia the different parts are vestibulum, labia majora and minora, and clitoris.
- Vestibulum last part of the genital tract. On its border there is the opening of the external
urethra. This location is marked by a fold called hymen. The walls of the vestibulum have glands of
Bartholin that produce a viscous secretion.
- Labia majora and minora the majora are well developed in livestock. During oestrus they are
enlarged. Both majora and minora have many glands producing lubricant to facilitate copulation.
- Clitoris homologue of the penis, with erective tissue and sensor nerve vessels.
,THE DOG UTERUS IS VERY SIMILAR TO THAT OF THE CAT
CHAPTER 1 – MALE ANATOMY
Components of the reproductive tract
Testes
They are they primary reproductive organs, produce gametes and male sex hormones (androgens). Each
testis consists of many tubuli seminiferi surrounded by a layer of connective tissue called tunica albuginea
(vedi anche capitol 5). The sperm cells are produced in the tubuli seminiferi; they are composed by a basal
membrane, a layer of Sertoli cells and germ cells (vedi prima figura capitol 5). The connective tissue
between the tubuli seminiferi contains Leydig cells, which produce androgens (hormones).
The testes are located in a fold of the peritoneum called tunica vaginalis (under the skin), and are
surrounded by the scrotum. They are more or less outside of the body, so their temperature is lowered of
4-7°C compared to the body, to allow optimal functioning. The scrotal skin contains many sweat and
sebum glands, and contains almost no subcutaneous fat. Two muscles (cremaster muscle and tunica
dartos) can lower or raise the scrotum. The vascular system in the spermatic cord forms a pampinoform
plexus where the artery and veins exchange heat in a counter-current flow. In addition, temperature
receptors in the scrotal skin stimulate panting and sweating, to decrease body temperature. All these
characteristics just mentioned are important for the thermoregulation of the testis.
Epididymis
After being produced in the tubuli seminiferi, sperm cells pass in the rete tubules and efferent ducts. Then
they enter in the head (caput) and body (corpus) of the epididymis. Here spermatozoa mature and become
fertile. After several days of transport through the epididymis, they enter the tail (cauda) of it, where they
are stored. (there is one epididymis for each testicle)
Ductus deferens
It is the draining duct of the epididymis. There is
one for each testicle. The last part of the duct,
called ampulla, takes care of secretions and
transport. It is absent in boar and cat.
, Accessory glands
They include:
- ampulla of the ductus deferens, absent in boar and cat
- vesicular glands, absent in dog
- prostate, body absent in ram; disseminate prostate absent in stallion
- bulbo-uretheral glands (Cowper’s glands), absent in dog and predominant in boars.
these glands produce fluids (the seminal plasma) that will mix with sperm cells before ejaculation. They
contain sugars, proteins, enzymes, hormones, minerals and antimicrobial compounds. Some functions are
nutrition and protection of sperm cells and improvement of seminal transport through the female tract.
Penis
It is divided into glans penis, body and crura. It has a cavernous body surrounded by thick connective
tissue, the tunica albuginea. Erection of the penis is needed before intromission in the vagina. It is a
consequence of the increased blood flow, due to dilatation of the arteries that supply blood to the
cavernous body. In stallions there is increase in size and length; in ruminants and boars it is mainly
straightening of the retractor penis muscle, so there is only elongation.
Prepuce
It is divided into a penile (embedding the penis) and a pre-penile part. The epithelium of the penile part is
connected with the penis integument at birth. A few weeks after birth this connection disappears, and the
penis is freely embedded in the prepuce. If the connection does not disappear, intromission in the vagina is
very difficult or impossible; this abnormality is heritable and is called persistent frenulum.
CHAPTER 2 – FEMALE ANATOMY
Components of the female reproductive system:
Two ovaries
Primary reproductive organs, located in the abdominal cavity. They produce female reproduction hormones
(estrogens and progesterone) and contain the oocytes. The shape and size of the ovaries are strongly
dependent on the activity of the pituitary land that produces LH and FSH, which stimulate follicle
development, ovulation and corpus luteum development.
Reproductive tract
It is a tubular structure consisting of (from inside to outside):
- Endometrium a mucosa layer of epithelial cells and a submucosa layer containing blood vessels
and uterine glands
- Myometrium two muscle layers consisting each of an intermediate layer rich in blood vessels, a
circular layer of smooth muscle and a longitudinal layer
- Mesometrium serosa layer of connective tissue
The length of the reproductive tract depends on species, e.g. the oviduct can be 15-30cm based on species,
uterus horns are longest in sows (60-90cm), vagina can be 10-35cm.
Different parts of the tract:
- Oviducts long and coiled tubes that connect the ovaries to the uterus. It can be divided into:
o Infundibulum the abdominal end on the oviduct (ovarian bursa), with fimbriae that
surround the ovaries
o Ampulla more distal part of the oviduct (it is right after the infundibulum near the
ovaries), where fertilisation takes place
o Isthmus the last part connected to the uterus with the utero-tubal junction UTJ
- Uterus consists of two uterine horns (cornua uteri), a uterine body (corpus uteri) and the cervix.
The relative size of the uterine body and the horns varies between species. There are different
types of uteri:
o Uterus duplex both horns are completely split, no uterine body is present and there are
2 cervices, e.g. in rabbit
o Uterus bicornuate with two poorly developed (mare), moderately developed (cow) or
highly developed (sow, bitch, queen) uterine horns. There is only one cervix
o Uterus simplex with a prominent uterine body and no uterine horns (humans).
The endometrium is important to regulate cyclicity and embryonic development. The glands of the
endometrium are in the epithelium of the uterus; they are small during oestrus but grow and
increase their secretions during progesterone dominance. Also the endometrium itself produces
secretions important for survival and capacitation of sperm cells, development of embryo and
luteolysis (elimination of corpus luteum if there is no pregnancy).
The endometrium of the cow and ewe contain about 100 non-glandular protrusions called
caruncles, important for adhesion of the placenta during pregnancy. The myometrium is important
for transport of sperm cells and expulsion of foetus.
, Functions of the uterus sperm transport to oviducts, transport of embryo to the site of
implantation, luteolysis and control of cyclicity, providing nutrition and gas exchange to the
embryo, expulsion of foetus at parturition.
- Cervix it has a thick muscular wall and is a sphincter-like organ. It is a barrier that closes the
connection between uterus and environment, because smooth muscles in it contract to prevent
passage of microorganisms. It has many folds which can be in a spiral (ruminants) or adapted to the
corkscrew-like penis of pigs. It also has many glands that produce mucus; during pregnancy, a thick
mucus closes the cervix to prevent bacterial entrance in the uterus.
Functions semen transport, semen reservoir, selection of fertile sperm cells.
- Vagina connects cervix and outer genital opening. It does not have many glandular cells and the
musculature is less developed. The caudal end of the vagina hosts the opening of the urethra. In
cattle and sheep, semen is deposited here while in pigs it is deposited in the cervix and in horses in
the uterus. The vagina also can act as barrier against microorganisms. Most animals have only one
vagina, but marsupials have two: one to transport sperm and one to transport the embryo to the
pouch.
External genitalia the different parts are vestibulum, labia majora and minora, and clitoris.
- Vestibulum last part of the genital tract. On its border there is the opening of the external
urethra. This location is marked by a fold called hymen. The walls of the vestibulum have glands of
Bartholin that produce a viscous secretion.
- Labia majora and minora the majora are well developed in livestock. During oestrus they are
enlarged. Both majora and minora have many glands producing lubricant to facilitate copulation.
- Clitoris homologue of the penis, with erective tissue and sensor nerve vessels.
,THE DOG UTERUS IS VERY SIMILAR TO THAT OF THE CAT
CHAPTER 1 – MALE ANATOMY
Components of the reproductive tract
Testes
They are they primary reproductive organs, produce gametes and male sex hormones (androgens). Each
testis consists of many tubuli seminiferi surrounded by a layer of connective tissue called tunica albuginea
(vedi anche capitol 5). The sperm cells are produced in the tubuli seminiferi; they are composed by a basal
membrane, a layer of Sertoli cells and germ cells (vedi prima figura capitol 5). The connective tissue
between the tubuli seminiferi contains Leydig cells, which produce androgens (hormones).
The testes are located in a fold of the peritoneum called tunica vaginalis (under the skin), and are
surrounded by the scrotum. They are more or less outside of the body, so their temperature is lowered of
4-7°C compared to the body, to allow optimal functioning. The scrotal skin contains many sweat and
sebum glands, and contains almost no subcutaneous fat. Two muscles (cremaster muscle and tunica
dartos) can lower or raise the scrotum. The vascular system in the spermatic cord forms a pampinoform
plexus where the artery and veins exchange heat in a counter-current flow. In addition, temperature
receptors in the scrotal skin stimulate panting and sweating, to decrease body temperature. All these
characteristics just mentioned are important for the thermoregulation of the testis.
Epididymis
After being produced in the tubuli seminiferi, sperm cells pass in the rete tubules and efferent ducts. Then
they enter in the head (caput) and body (corpus) of the epididymis. Here spermatozoa mature and become
fertile. After several days of transport through the epididymis, they enter the tail (cauda) of it, where they
are stored. (there is one epididymis for each testicle)
Ductus deferens
It is the draining duct of the epididymis. There is
one for each testicle. The last part of the duct,
called ampulla, takes care of secretions and
transport. It is absent in boar and cat.
, Accessory glands
They include:
- ampulla of the ductus deferens, absent in boar and cat
- vesicular glands, absent in dog
- prostate, body absent in ram; disseminate prostate absent in stallion
- bulbo-uretheral glands (Cowper’s glands), absent in dog and predominant in boars.
these glands produce fluids (the seminal plasma) that will mix with sperm cells before ejaculation. They
contain sugars, proteins, enzymes, hormones, minerals and antimicrobial compounds. Some functions are
nutrition and protection of sperm cells and improvement of seminal transport through the female tract.
Penis
It is divided into glans penis, body and crura. It has a cavernous body surrounded by thick connective
tissue, the tunica albuginea. Erection of the penis is needed before intromission in the vagina. It is a
consequence of the increased blood flow, due to dilatation of the arteries that supply blood to the
cavernous body. In stallions there is increase in size and length; in ruminants and boars it is mainly
straightening of the retractor penis muscle, so there is only elongation.
Prepuce
It is divided into a penile (embedding the penis) and a pre-penile part. The epithelium of the penile part is
connected with the penis integument at birth. A few weeks after birth this connection disappears, and the
penis is freely embedded in the prepuce. If the connection does not disappear, intromission in the vagina is
very difficult or impossible; this abnormality is heritable and is called persistent frenulum.
